Using the White Balance Tool in Adobe Photoshop Lightroom 4

Martin Evening shows you how to use the Temp and Tint sliders in the White Balance tools (WB) section to precisely adjust the white balance of a photograph. With these you can color-correct most images or, if you prefer, apply alternative white balances to your photos.

From the book

White Balance tool

The Temp and Tint sliders in the White Balance tools (WB) section can be used to precisely adjust the white balance of a photograph. With these you can color-correct most images or, if you prefer, apply alternative white balances to your photos. The White Balance tool is located near the top of the Basic panel. You can activate the tool by clicking on it or by using the shortcut. This unlocks the tool from its docked location and allows you to click anywhere in the image to set a new white balance (Figure 4.20). The floating loupe magnifier provides an extreme close-up of the pixels you are measuring, which can really help you select the correct pixel reading. As you hover over an image, you will also see the RGB readout values for the point immediately beneath the cursor (see Figure 4.21), as well as at the bottom of the Histogram panel. These RGB readings are shown as percentage values and can help you locate and check the color readings (if the RGB values are all close enough to the same value, the color can be regarded as neutral). If the Auto Dismiss option is disabled in the Toolbar (see Step 1 below), all you have to do is click to activate the White Balance tool and continue clicking with the tool until you find the right setting. You can then use the key or the key again to cancel working with the White Balance tool and return it to its normal docked position in the Basic panel.

Figure 4.20. To activate the White Balance tool, click the tool to undock it from the panel.

Figure 4.21. Instead of using the traditional 0 to 255 scale, the RGB readouts are given as percentages. You can determine the neutrality of a color by how close the readout numbers are to each other.

To make a white balance adjustment, select an area of the picture that should be neutral in color (but not a bright white area). The light gray stone in this photo is a perfect spot to sample from. If the Auto Dismiss box (circled) in the toolbar is checked, the White Balance tool automatically returns to its docked position in the Basic panel after a single click. If the Auto Dismiss box is unchecked, you can click and keep clicking with the White Balance tool until you are completely satisfied with the white balance adjustment that you have made.

The Show Loupe check box allows you to toggle displaying the loupe that appears below the White Balance tool cursor. You can adjust the loupe scale setting by dragging the slider next to the Show Loupe item in the toolbar. This slider adjusts the sample grid pixel size, and dragging the slider to the right increases the number of pixels used when sampling a white balance point measurement. Increasing the pixel sample size can be beneficial if you want to aggregate the pixel readings more, such as when you’re sampling a really noisy image and you don’t want the white balance measurement to be unduly affected by the pixels that contain color noise or other artifacts. But note that the White Balance tool sample size area now samples an area that is dependent on the zoom setting. In other words, the White balance sample area is now zoom-level dependent.

Do we still need the 0 to 255
scale in the readout section?
I know some people say that they
would like to see this as an
option, but there are no real
valid reasons for doing so. The
0 to 255 scale has only come
into existence because of the
way the number of levels are
calculated for pixel rendered
8-bit images. The percentage
scale (in my view) makes it easier
to interpret what the eyedropper
readout numbers mean. Having
said that, when you view a photo
with Soft Proofing turned on
the RGB numbers in the Histogram
display using the 0 to 255 scale
(see pages 471 to 476).

White Balance corrections

In most shooting environments, once you have found the right white balance, all the other colors will tend to fit into place. You can help get the white balance right in-camera by choosing a fixed or auto setting. Or, you can use a white balance or color checker chart like the one shown in Figure 4.22 as a preparatory step that will help you make a more accurate, measured reading later in Lightroom. A camera auto white balance setting may do a good job, but it really depends on the camera you are using, because even the best cameras won’t know how to handle every lighting situation. In Figure 4.23 we see a scene where there were mixed lighting conditions. This photograph could be processed for either the exterior daylight or the tungsten lighting indoors, and each could be said to be correct. In situations like this you can’t always rely on the camera’s Auto White Balance setting and you’ll have to decide for yourself which setting works the best. This is where the White Balance tool can come in handy. The trick is to analyze the picture and look for an area in the scene that should be a neutral, nonspecular, textural highlight. You should aim to select something that should be a neutral light gray, because if you click on an area that’s too bright, there may be some clipping in one or more of the color channels, which can result in a false white balance measurement and consequently make an inaccurate adjustment.

Figure 4.22. Among other things, the X-Rite Gretag Macbeth ColorChecker chart is useful for taking white balance readings under the same lighting conditions as those you are about to shoot with. To take a white balance reading in Lightroom, click on the light gray patch next to the white patch.

Figure 4.23. The white balance can be measured manually by selecting the White Balance tool () and clicking on an area in the image that should be near white in color. This image shows two possible white balances: one measured for the indoor lighting (left) and one measured for the outside daylight (right).

NOTE

It is tempting to assume that the grayscale patches in the X-Rite Gretag Macbeth ColorChecker chart shown in Figure 4.22 correspond to the full tonal range that you are trying to optimize using the Basic and Tone Curve panel controls. This is a dangerous assumption to make because in a properly optimized image, the white and black patches rarely ever equate to the respective highlight and shadow points in the image. For example, the black patch in the ColorChecker is really a dark gray, and if you were to clip the shadows using this patch as your guide you could end up clipping a lot of important shadow information.

Understanding White Point

The adjustments made using the White Balance slider controls in the Basic panel will have the greatest impact on the overall color appearance of an image (Figure 4.24).

Figure 4.24. The White Balance slider controls in the Basic panel allow you to manually adjust the white point in an image. The Temperature slider adjusts the white point from warm artificial lighting conditions to cool daylight and beyond. The Lightroom slider represents this as a progression going from blue to yellow. The Tint slider allows you to fine-tune the white point for any green/magenta bias in the white point.

The numbers used in the Temp slider refer to the temperature scale measured in degrees Kelvin, which in photography is commonly used when describing the color temperature of a light source. Artificial lighting, such as a tungsten lamp light source, is said to have a color temperature of around 2800 to 3200 K, whereas average daylight is notionally rated as being 5000 K and overcast daylight is somewhere around 10000 K. As a result, photographers often tend to describe higher color temperature lighting conditions as being “cooler” and the lower color temperature lighting conditions as being “warmer,” because most people equate blue colors with coldness and reddish colors with warmth (although technically speaking, a bluer color temperature is actually hotter). The Temperature slider scale allows you to set what “should be” the white point of the image based on the Kelvin scale. Some people get confused on this point because they assume that if 3200 K equates to tungsten-balanced film and 5500 K equates to daylight-balanced film, dragging the Temperature slider to the right makes the image cooler and dragging it to the left makes it warmer. In fact, the opposite is true. The key point to emphasize here is that the White Balance controls are used to “assign” the white point as opposed to “creating” a white balance. Dragging the slider to the right makes the image warmer and dragging it to the left makes it cooler. Try thinking of it this way: if you have a photograph shot under average daylight conditions and assign a lower color temperature to the photo, like one more suited for tungsten lighting conditions, such as 3200 K, then naturally enough, the colors in the image will appear blue. The result of this experiment is exactly the same as using a tungsten-balanced film emulsion to record a daylight scene.

Tint adjustments

You don’t always need to make Tint slider adjustments when color correcting an image and when you do these can usually be quite minor, except for those situations where the light source emits uneven spectral wavelengths of light, such as when shooting under fluorescent lighting. It is always hard to set an accurate white point for these types of lighting conditions, but fluorescent lighting conditions usually require a heavy magenta tint bias to the white point in order to remove the strong green cast.